Recent content by Waramanga

Hi all, Is anyone out there using revit for construction phase engineering? ie fan calcs, pump calcs etc? Seems to have a lot of promise. I am and engineer working for a contractor and our drafting is all outsourced (Revit) and then we do the calcs based on the 2d pdfs of the project. Seems...

Get your hands on insertion loss data for internally lined duct to determine what length of treatment you need. I agree that a mech engineer should be able to handle 90% of HVAC acoustic design situations.

Hi all, I have a job I need to recommission that has Crane valves, specifically D930 model double regulating type (they are branded "John" which I understand was a local Australian company that licensed them to sell in Australia at one stage about 20 years ago). I cant find any data on the...

Yes it will have to be a VSD, just adjust until the flow is correct and ignore the static pressure.

The OP doesn't think this is straight forward clearly. I am not familiar with ASHRAE notation, what is the C value and what formula do you use it in?

I have a constant volume system on a 3 storey building that we are decommissioning floor by floor. Still need the pressure to feed each floors mixing boxes but 1/3 less volume. Change the pulley to suit etc etc..... any ideas??

They assume one variable is changing at a time. Volume proportional to speed, pressure to the square of the speed, I want to keep the pressure constant and change the volume. Which fan law covers that situation Willard?

Hi All, How do I calculate fan RPM required to maintain constant pressure and halve the volume? If I assume constant resistance to airflow in the system its just a proportional relationship ie half the volume is half fan RPM but the system resistance is going down by the square root of the...

Agreed, BAS quality is completely dependant on the local support for all but the most complicated systems in my experience. Around here the installers install for nothing and charge like wounded bulls for service, fitouts etc. The best you can hope for is good service while you are getting...

If the rooms are not heated then stratification wont happen, if you are heating the room then normal engineering principals apply, whats the point of heating the ceiling eh?

Missed that you were after fixed pressures. What is the application?

Yes you will need to provide a path for the air to get out of the room and outside. If the resitance path is too great then you will end up with doors that don't open, front doors howling etc. Maybe you should look at heat recovery and a return air fan? usually pays for itself up front.....

+1 Willard, OP needs professional assistance.

Err, document on the internet?? I think you are in trouble designing the chilled water system if you are struggling with the make-up....ask a local plumbing consultant for advice on this, money well spent mate!

1. All motors for hvac are synchronous, ie they rotate at a speed dependant on the line frequency and the number of poles the motor has. If you have a giant motor driving a tiny fan it will spin at the same speed as the right sized motor on the same fan (assuming the same number of poles. 2...